1. Field of the Invention
The present invention relates to the field of mass spectrometric detection, in particular, to a mass calibration kit and a correction method for a low-mass area of a high-resolution mass spectrometer in a negative ion mode.
2. Description of Related Art
MALDI refers to a matrix-assisted laser desorption/ionization mass spectrometry. Mass spectrometers of such type are widely applied to accurate mass measurement on various sample molecules. In such technology, sample molecules usually need to be mixed with a type of organic small molecules. The organic small molecules of this type include functional groups capable of absorbing laser energy and transfer the energy to the sample molecules to vaporize and ionize them, which are finally detected by a detector.
In an existing MALDI mass spectrometry technology, a small-molecule organic acid is usually used as a matrix. Major disadvantages of such a method include: (1) a series of background peaks are usually generated in the low-mass area; (2) sizes of crystal particles are inconsistent; and (3) low-mass sample signals are suppressed. In addition, the matrix causes serious contamination to the ion source, which not only ruins a quantitative relationship between the absolute signal intensity of the mass spectrum and the sample quantity, but also affects the spatial resolution. Because of the foregoing reasons, the MALDI mass spectrometer cannot analyze low-mass molecules by using a common matrix, especially in a negative ion mode. Currently, there is no commercialized calibration kit. Therefore, such low-mass molecules cannot be analyzed by using MALDI.